- LR-I and precursor B-cell acute lymphoblastic leukemia (ALL) HR-S and HR-I: Patients receive cyclophosphamide IV over 30 minutes on days 50 and 64; mHD IV over 24 hours on days 51, 65, 78, and 92; etoposide phosphate IV over 1-2 hours and cytarabine IV over 1 hour on days 80 and 94; oral mercaptopurine on days 64-70 and 92-98; oral thioguanine on days 78-84; and methotrexate IT on days 29, 51, 65, 78, and 92. All precursor B-cell ALL patients with a detectable MRD load on day 29 and T-cell ALL patients with an MRD load ≥ 10³ on day 29 are randomized* (randomization 1) to 1 of 2 arms to receive cytarabine and pegaspargase vs. clofarabine and pegaspargase.